Automatic telephone-exchange system.



C. L. GOODRUM.

AUTOMATIG TELEPHONE EXEHANGE SYSTEM APPLICATION FILED APR.27| I916.

' Patented Aug 28. 191?,

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CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented An 28, 1917.

Application filed April 27, 1916. Serial No. 93,868.

T 0 all whom it may concern:

Be it known that 1, CHARLES L. GooDRUM, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to automatic telephone exchange systems, and more particularly to circuit arrangements and means for stepping automatic switches, utilized in such systems.

One feature of this invention resides in the provision of a relay which is arranged to be connected to a stepping magnet circuit and which by shunting its own winding, controls the repeated energization of the stepping magnet.

Another feature resides in the provision of a common stepping relay for a plurality of stepping magnets.

The drawings represent diagrammatically a portion of a telephone exchange system, employing the present invention. Only so much of the circuit arrangements and apparatus is shown as is necessary for a clear understanding of this invention.

The mechanical construction and the operation of the step-by-step selector switches and other apparatus used in building up a connection between a calling and a called line are well known to those skilled in the art, and, therefore, in the present disclosure a detailed description will be given only of the operation of a selector switch utilized in the establishment of a connection.

The subscriber at substation 1, desiring to establish a connection with substation 2, removes his receiver from the switchhook and causes a trunk finder or line switch 3 to select, in a well-known manner, an idle trunk leading to a selector switch 1. As soon as the wipers of switch 3 are set on the terminals of an idle trunk, a circuit is closed from grounded battery 5 through the left-hand winding of a line relay 6, wiper 7 of a side switch associated with selector 1-, the loop of the calling substation 1, sideswitch wiper 8 and the right-hand winding of relay 6 to ground. Relay 6 upon energization closes a circuit from ground through its armature and front contact, side-switch wiper 11, and the winding of a quick acting escapement magnet 12, to grounded battery 18. Upon the energization of the escapement magnet 12, the wipers of the side-switch associated with selector t are moved into their second position.

The side switch used in this system is similar to that used in other systems, but differs therefrom in that in certain instances it moves on the energization instead of on the deenergization of the escape magnet.

The calling subscriber now operates his calling dial 20 to interrupt the line circuit a desired number of times to cause the setting of the selector switch 4. Upon each interruption of the line circuit, line relay 6 releases its armature and closes a circuit for the primary operating magnet 15, which moves the brushes of selector switch 1 from group to group in a well-known manner. The circuit of magnet 15 may be traced from grounded battery 14, winding of magnet 15, back contact and right-hand armature of a slow-acting relay 16, side-switch wiper 17 and the back contact and armature of relay 6, to ground.

As relay 16 is slow to pull up, it will not become energized during the vibration of the armature of relay 6. As soon, however, as the sending out of impulses ceases and the armature of line relay 6 is maintained attracted, a circuit is closed from ground, through the armature and front contact of relay 6, side-switch 'wiper 11, contact 21 (closed as soon as the brushes of selector switch 4: leave their normal position), and the left-hand winding of slow-acting relay 16 to grounded battery 22. Relay 16 becomes encrgized, disconnects magnet 15 at its right armature and closes a circuit from grounded battery 13 through the winding of escapement magnet 12, left-hand armature and front contact of relay 16 and front contact and armature of relay 6, to ground. The side-switch wipers are then moved to third position.

In the present invention, secondary stepping magnets 25, 25 and 25 of a group of selectors shown at the lower right corner of the drawings are successively energized through a circuit controlled by a common stepping relay 23. The stepping magnets have low resistances and their armatures are heavy so that they will not hold up through the relatively high resistance of'the stepping relay. The stepping relay 23 is slow to re lease and its armature is lightly tensioned. (hen the escapement magnet moves the side-switch wipers into position 3 a circuit is completed from grounded battery 1% through secondary stepping magnet 25, Wiper 2e, and stepping relay 23 to ground. Stepping relay 23 then attracts its armature and completes a shunt circuit about its winding, thus so decreasing the resistance of the circuit that stepping magnet 25 is energized. The winding of stepping relay 23 being now deprived of current, it releases its armature and interrupts the shunt circuit. Thereupon the stepping relay is again energized and attracts its armature. 1t will be noted that the interruption of the shunt circuit introduces the relatively high resistance of stepping relay into the circuit. This so reduces the current through the stepping magnet that it retracts its armature. vVhen the shunt circuit is completed, this resistance is removed and the stepping magnet is actively energized and attracts its heavy armature. This repeated making and breakin of the shunt circuit continues until an idTe trunk is reached. It will be seen that a circuit for the stepping magnet exists at all times while the side switch is in position 3 but the high resistance of relay 23 is intermittently included and shunted from the circuit of the stepping magnets.

Under the control of magnet 25, the wipers of the selector switch are stepped from trunk to trunk until an idle trunk is reached. WVhen the side-switch wiper 11 moved out of its second position, relay 16 became deenergized and opened the circuit of escapement magnet 12. As soon as test brush 26 of selector switch l reaches the terminal of an idle trunk to which ground will be connected, a circuit is closed from this ground connection through brush 26 of selector 4:,

conductor 27, side-switch wiper 30, the back 7 contact and left-hand armature of relay 16, and the winding of escapement magnet 12, to grounded battery 13. The magnet 12 will be energized causing the wipers of the sideswitch to move into position at, in which position the calling substation line is eX- tended through the wipers 7 and 8 of the side switch to another switching mechanism provided between selector at and the called substation 2. The rest of the desired connection may be established in any wellknown manner.

lV'hen the called subscriber replaces his receiver on the hook, the succeeding switching apparatus (selector or connector) will be restored to normal, causing ground to be placed upon the conductor engaged by brush 26. This will close a circuit from ground through brush 26, conductor 27, armature and back contact of magnet 12, (this magnet being deenergized in the fourth position of the side-switch), side-switch wiper 31 and the winding of release magnet 32, to grounded battery 33. Release magnet 32, upon energization, closes a locking circuit for itself from grounded battery 33, through its winding and contact 31, and off-normal contact 35 of selector switch 4: to ground. Under the control of the release magnet 32, the selector switch l and the associated side switch will be restored to normal, the locking circuit of the release magnet being maintained closed at contact 315 until selector switch 1 has been restored to its normal position. After the receiver at the calling substation 1 has been hung up and the side switch has been restored to normal, a ground is sent through the armature and back contact of relay 6, side-switch wiper 17 and off-normal contact 36 to the trunk finder 3, for causing the release of this switch.

Should the subscriber at substation 1 abandon the call before sending out impulses, he would hang up his receiver and cause thereby the deenergization of relay 6. A circuit would be closed thereupon from ground through the armature and back con tact of relay 6, the side-switch wiper 17 (which is now in position 2), and the righthand winding of slow-acting relay 16, to grounded battery 22. The slowacting relay 16 by pulling up its armature closes a circuit from grounded battery 33 throughthe winding of release magnet 32, the front contact and right-hand armature of slowacting relay 16, the side-switch wiper 17,

and the back contact and armature of relay 6, to ground. The release magnet 32 causes the restoration of the switching mechanism in the same manner as above described.

It the subscriber at substation. 1 abandons the call in position 3 of the side-switch wipers, that is to say, after the operation of magnet 15, the release would be accom-- plished in the same manner as in the last mentioned case.

/V hat is claimed is:

1. In a telephone exchange system, incoming and outgoing groups of lines, a selector switch for extending an incoming to an outgoing line, brushes for .aid selector switch, directively controlled means for moving said brushes in operative relation to a group of outgoing lines, a stepping magnet for moving said brushes of said selector switch over busy lines in the selected group, a relay in series with said stepping magnet for controlling the actuation thereof, a winding for said relay, and means for 010s ing a shunt circuit about said relay winding upon its actuation.

2. A circuit including a relay having a high resistance winding, a stepping magnet winding in series with said relay, and a shunt closed about the winding of said relay upon its actuation.

3. The combination with a plurality of stepping magnets, of a stepping relay successively connected in series with said magnets, and resistance shunting means associated with said stepping relay for controlling the operation of said magnets.

i. The combination with a stepping magnet having a winding of low resistance, of a stepping relay having a high resistance winding in scries with said magnet winding and a shunt circuit about said stepping relay winding completed by the energization oi said stepping relay.

5. In combination, a selector switch, a stepping magnet therefor, a winding for said magnet, a relay having a winding of relatively high resistance arranged to be included in series with said magnet, an armature for said relay and circuit connections whereby said armature upon attraction short-circuits said relay windin 6. In combination, a group of selector switches, stepping magnets, one for each switch, windings for said magnets, respectively, a stepping relay, a winding of relatively high resistance for said relay, means for connecting any of said magnet windings in series with said relay winding, an armature for said relay and circuit connections whereby said armature upon attraction short-circuits said relay winding.

In witness whereof, I hereunto subscribe my name this 26th day of April, A. 1)., 1916.

CHARLES L. GOODRUM.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patent& Washington, D. G. 

